FBI personel gather in a secured area near the Borderline Bar and Grill where a Marine veteran opened fire and killed 12 people. Photo by Jim Ruymen/UPI | License Photo

Nov. 11 (UPI) -- The suspected gunman in last week's shooting at a Thousand Oaks, Calif., bar died of a self-inflicted gunshot wound to the head, his autopsy confirmed.

Dr. Christopher Young, the Ventura County chief medical examiner, said his office was conducting toxicology tests to determine whether Ian David Long, 28, had any drugs in his system at the time of the shooting Wednesday at Borderline Bar and Grill.

Police said Long opened fire at the crowded bar late Wednesday, killing 12 people, including a sheriff's deputy who responded to the initial 911 calls. The .45 caliber handgun he used was purchased legally.

Capt. Garo Kuredjian said the sheriff's office conducted a search warrant at Long's residence in Newbury Park and carried out a search of his vehicle. They have not determined a motive for the shooting.

"We're going to exhaust every investigative means possible," Kuredjian said. "We won't know until we see where the evidence leads."

The family of one of the victims, Sgt. Ron Helus, scheduled his memorial service for Thursday at a church in Westlake Village. A procession will transport his casket to a graveside service at Pierce Brothers Valley Oaks Mortuary and Cemetery.